1. Field of the Invention
The present invention relates to preparation of polychlorinated pyridine mixtures by direct liquid phase chlorination of pyridine or pyridine hydrochloride. Typical of the products produced are 2-chloro-, 3-chloro-, 2,6-dichloro-, 3,5-dichloro, 2,3,5-trichloro, 2,3,6-trichloro-, 3,4,5-trichloro, 2,3,4,5-tetrachloro-, 2,3,5,6-tetrachloro- and 2,3,4,5,6-pentachloropyridine. These products have utility, for example, as intermediates for herbicides and insecticides. A further aspect of the present invention relates to the separation of these mixed chloropyridines and then further chlorination to yield valuable higher chlorinated pyridines such as 2,6-dichloro-, 2,3,5-trichloro-, 2,3,6-trichloro-, and 2,3,5,6-tetrachloropyridine.
2. Description of the Prior Art
The utility of 2-chloropyridine as an intermediate to fungicidal and bactericidal compositions is described by Bernstein et al U.S. Pat. No. 2,809,971 and by McClure et al U.S. Pat. No. 3,159,640. In Orvik U.S. Pat. No. 4,275,212 and Fah et al U.S. Pat. No. 4,287,347, the utility of 2,3,5-trichloropyridine is described as an intermediate for herbicidal compositions. Bowden et al U.S. Pat. No. 4,108,856 describe a vapor phase chlorination process for producing 2,3,5-trichloropyridine from 3,5-dichloropyridine. 2,6-dichloropyridine is catalytically chlorinated in the liquid phase at greater than 180.degree. C. to yield the valuable insecticidal intermediate 2,3,5,6-tetrachloropyridine in Smith et al U.S. Pat. No. 3,538,100.
The conversion of 2,3,6-trichloropyridine to 2,3,5,6-tetrachloropyridine by liquid phase ferric chloride catalyzed chlorination is taught by Dietsche et al U.S. Pat. No. 4,256,894.
Weis et al U.S. Pat. No. 4,258,194 describe a process for producing 2,3,5-trichloropyridine from 2,3,4,5-tetrachloropyridine. The valuable insecticidal intermediate 2,3,5,6-tetrachloropyridine is produced from 2,3,4,5,6-pentachloropyridine in a process described by Weis U.S. Pat. No. 4,259,495.
Brewer et al U.S. Pat. No. 3,732,230 describes a liquid phase chlorination of pyridine hydrochloride at temperatures from about 130.degree. C. to about 175.degree. C. with greater than 30 psig hydrogen chloride partial pressure in the reactor. The chief reaction products are 2,3,4,5-tetrachloropyridine, 2,3,5- and 3,4,5-trichloropyridine, small amounts of 3,5-dichloropyridine and a dimer polymer of pyridine.